"Custom Template" messaging and notifications / prep for 2.0.0 breaking changes

[richaber]

WPSWA v 2.0.0 will upgrade all the bundled Algolia JS components (ref #116), which will affect customized templates.

We need to approach this with messaging that will let WPSWA users know what is happening, before 2.0.0 drops.

in_plugin_update_message-{$file} and after_plugin_row_{$plugin_file} can be used in conjunction with the readme file's == Upgrade Notice == to help deliver messaging about these changes before we release 2.0.0.

We should add a page in the Wiki with details about the breaking changes.

The template version utility code and related admin notice code should be completed, though we should not show the "Your template version is out of date" notice until we ship 2.0.0.

[richaber]

WPSWA version 2.0.0 Upgrade Notice added as pinned issue #143
WPSWA version 2.0.0 Upgrade Notice also added to Wiki homepage

[richaber]

WPSWA 1.8.0 just released with the template notices and major version update notices.

Although we cannot control how users receive 2.0.0, I feel we have done our due diligence, and 1.8.0 should at least help ease the transition for some users.

[richaber]

WP Search with Algolia version 2.0.0 has been tagged and released.

https://github.com/WebDevStudios/wp-search-with-algolia/releases/tag/2.0.0

https://plugins.svn.wordpress.org/wp-search-with-algolia/tags/2.0.0/

[richaber]

Major Version Update Notification worked as intended: